Shift from anti-to proinflammatory cytokine profiles in microglia through LPS-or IFN-γ-mediated pathways

In this study, cytokine mRNA profiles in microglia from newborn rats were detected by in situ hybridization. Under natural culture conditions, microglia expressed the immunosuppressive transforming growth factor-β1 (TGF-β1) and interleukin (IL) 10 to a greater degree than the pro-inflammatory cytokines IL-1β, IL-6, IL-12, interferon-γ (IFN-γ) and TNF-α. High TGF-β1 and IL-10 levels could reflect one mechanism for immune privelege within the CNS under physiological conditions. Stimulation of microglia with LPS or IFN-γ resulted in strong up-regulation of proinflammatory cytokines, while TGF-β1 and IL-10 were down-regulated. These effects of LPS or IFN-γ are anticipated to reflect immunopathogenic processes within the CNS.